Tag Archives: rodents

The Subterraneans

Underground! From rabbit warrens to nuclear fallout shelters, it’s a great place to hide out. If you’re a terrestrial vertebrate, the safest place you could conceivably be is underground, where you’re protected by a temperature-stable bunker, an ocean of dirt, rocks, and roots. But it’s one thing to dig a burrow, and another to spend all your time underground, swimming through the soil. If you’re a full-time tunneler, there are really just two body types you can evolve to fit: the “mole” model, and the “earthworm” model.

Consider the difficulties of underground travel. You don’t want to be too large, or digging would be exhausting. You don’t want large eyes, which would be useless and become full of grit. You’ll need a keen sense of smell and touch, as you’re likely to be finding food by chemical and tactile signals rather than visual ones. This star-nosed mole from North America is a great example of the mole archetype: small, compact, wedge-shaped, with sealed-off eyes and ears, powerful front claws, and 22 fleshy appendages that are among the most sensitive touch receptors in the animal kingdom. Star-nosed moles are true swimmers; they breaststroke through soil, but are also quite adept at catching prey in the water. Moles are insectivores, related to that most ancient of mammals, the shrew. But thanks to the awesome power of convergent evolution, you don’t have to be related to the moles to become a mole.

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This is the story of a mythological animal. The animal itself is real, but the myth surrounding it is a species unto itself.

Lemmings are hamster-like rodents which live around the Arctic Circle in North America, Europe and Asia. They’re most notable for their fecundity — a female can produce litters of eight pups every five weeks — and for sustaining every carnivore in the Arctic. They don’t hibernate, but tunnel through the snow in the winter, ensuring that foxes, wolverines, snowy owls, ermines, lynxes, and wolves have a steady supply of food through the white months. Let’s be frank: Lemmings are the Tribbles of the Arctic. They are a fast-multiplying, too-cute food source, the ecological equivalent of tater tots. Sure, the species exists for its own purposes as well. But perhaps my carnivore allegiances are showing when I say that lemmings are a species that exists to be eaten. Without them, the Arctic ecosystem would collapse.

But one thing lemmings don’t do is commit mass suicide by jumping off cliffs. Every four years or so, the local lemming population goes into a sudden decline as the lemmings migrate to new territory in search of food. Along the way, they usually encounter bodies of water, and try to go around them. If they can’t, they’ll try to swim across them, and inevitably many of them drown. But the idea that lemmings are hard-wired to control their own booming populations by throwing themselves into the sea is ridiculous, the stuff of medieval legend. Yet that is the animal we know today, and it’s worth examining the mythological lemming. It teaches us much about ourselves.

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The problem with writing about animal “sin,” besides the fact that animals can’t sin, is that several of the Seven Deadly Sins could be categorized as “overindulgences,” which evolution often abhors. Eating more than you have to, for example, can slow you down, and is only useful when you’re threatened with starvation. The same is true for “greed:” why spend time accumulating things you don’t really need when you could be doing something useful, like foraging or fucking?

Yet there are hoarders. I don’t mean animals that cache food for later, like a squirrel. I mean animals that take, steal, and collect objects they don’t really need because it suits their fancy. And when you say “hoarder,” the first animal you probably think of is…

The Pack Rat. (Not to be confused with The Rat Pack.) Out here in the Western half of the U.S., pack rats collect sticks, grasses, animal dung and stones to build messy nests called middens, which are usually a foot or two high but can be over six feet tall. Notwithstanding the fact that a two-inch mouse doesn’t really need a house the size of a beaver dam, the “greedy” part about pack rats is their keen eye for shiny objects. If they encounter a piece of jewelry, they’ll often drop the stone they were carrying for this new bit of tinsel, lending them their other name, the “trade rat.”

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Land of the Lost

The other day we discussed adaptive radiation, the process by which a single ancestor can split into an aardvark, an elephant, a manatee and a mole. But how do species split from one another? Usually by being physically separated for a good amount of time. The obvious illustration would be a species radiating between islands, but “islands” can occur on land, too. Even within islands.

Rodents Of Unusual Size? I don’t think they… oh, there’s one.

Meet the Bosavi Woolly Rat, a cuddly cat-sized rodent and the largest rat in the world. What makes it remarkable isn’t just its size, but its location. It was discovered only last year in the Bosavi volcanic crater in Papua New Guinea, along with at least 40 other amazing animal species heretofore unknown to science and native only to this one crater, including a fanged frog, a fish that “grunts,” a marsupial called the Bosavi silky cuscus, a tree kangaroo, a new family of sleestaks, an ogre-faced spider that fishes for its prey, a new species of bat, the world’s smallest parrot, a new bird-of-paradise and caterpillars that collaborate to look like a snake. These creatures had no fear of humans, having probably never seen one before. After all, they’ve been walled inside an extinct volcano for 200,000 years.

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